With development of communications technologies, mobile communications networks and broadband radio access networks continuously evolve in their respective development directions, a wide variety of wireless networks emerge one after another, and different wireless networks have different features and service provisioning capabilities.
A next-generation wireless network is a heterogeneous network based on integration of multiple radio access technologies, including broadband wireless access, a cellular mobile communications system, a digital television broadcast network, and a satellite communications system. The heterogeneous network enables interconnection and interworking between different systems, so as to ensure that users can make full use of these heterogeneous radio access technologies, thereby satisfying various requirements of the users. For example, hybrid deployment of a secondary access network node (such as an SCN (small cell node)) and a primary access network node (such as an eNB (EUTRAN Node B, common base station)) forms a HetNet (heterogeneous network), where the secondary access network node has a small coverage area of cells, and the primary access network node has a large coverage area of cells. Compared with a HomoNet (homogeneous network) that includes only primary access network nodes, the HetNet features a greater throughput, a stronger capability of adapting to deployment scenarios, and the like, which can meet various requirements of the users.
In the HetNet, before a terminal interacts with a core network, not only physical connections need to be established between the secondary access network node and the primary access network node and between some core network nodes, but also tunnels that are used for transmitting user data need to be established on these physical connections. There are a variety of core network nodes: a core network control plane node, such as an MME (mobility management entity), and a core network user plane node, such as an SGW (serving gateway). The core network control plane node and the core network user plane node may be a same node, such as an SGSN (serving GPRS support node, GPRS (general packet radio service)). The terminal can interact with the core network nodes in the HetNet and the core network nodes in the HetNet can provide services for the terminal only after the tunnels are established.
In the prior art, there are mainly two manners of establishing a tunnel between a secondary access network node and a core network user plane node, as shown in FIG. 1A (the tunnel between the secondary access network node and the core network user plane node is transferred by a primary access network node) and FIG. 1B (the tunnel between the secondary access network node and the core network user plane node is not transferred by the primary access network node, but is a directly connected tunnel). A tunnel establishment manner in the primary access network node is fixed and switching between different tunnel establishment manners is not allowed. Therefore, only the tunnel establishment manner in either FIG. 1A or FIG. 1B can be selected, and switching between the two tunnel establishment manners is not allowed. However, if the primary access network node selects the tunnel establishment manner shown in FIG. 1A all the time, all user data between the secondary access network node and the core network user plane node passes through the primary access network node, which places higher pressures on a backbone network between the secondary access network node and the primary access network node, is likely to cause congestion, and further increases a delay in transmission of user data packets. Therefore, this increases a probability that the user data packets are discarded and deteriorates user experience. If the primary access network node selects the tunnel establishment manner shown in FIG. 1B all the time, when a terminal moves among different secondary access network nodes, a core network control plane node needs to receive and send path switching signaling, where the path switching instruction is used to process path switching caused by terminal moving; when there is too much path switching signaling that the core network control plane node needs to receive and send, a core network may break down and consequently an entire network cannot operate properly.